[Feature] Add custom build flags (like custom OpenGL version...)

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• The issue is specific to Raylib-cs and not raylib
• I checked there is no similar issue already reported
• My code has no errors or misuse of Raylib-cs

Issue description

I would love to see this feature in Raylib-cs, then we would have ANGLE support and it would possible to run a new or older version of OpenGL.

public static void SetOpenGLVersion(GlVersion version) {
      // Impliment it here
      // I would suggest doing a variable in the build that can be changed with code, so we can switch the Raylib.dll with the right OpenGL version.
}

Environment

OpenGL

[9ParsonsB]

@MrScautHD Have a look at the SQLite, SQLitePCL, & SQLitePCLRaw Nuget Packages

[MrScautHD]

So… How you want ro implement it?